Various types of battery packs for electric vehicles have been commercially available for years. A standard battery pack for an electric vehicle includes a container that houses multiple battery cells. The container also houses conductors that wire the battery together, as well as any wiring relays, in addition to the battery cells. Because of the presence of sensitive electrical components, the interior of a standard battery pack container must be free of water, debris and other elements that can cause electrical disturbances or electrical shorts. As such, a standard battery pack container is typically air-tight and water resistant so as to protect the battery cells from damaging external elements.
One of the main drawbacks of conventional battery packs for electric vehicles, however, is the inability to easily gain access to the individual battery cells within the battery pack container. Conventional battery packs are sealed tight and are not built to allow the container to be opened to gain access to the battery cells inside. This can become a problem when individual battery cells within the battery pack container become damaged or malfunctions. Under the conventional configuration, when a single battery cell in the battery pack container becomes damaged or expended, the consumer's inability to replace the sole damaged battery cell requires the consumer to discard the entire battery pack and purchase a new one. This is wasteful and time-consuming.
The above drawback is compounded in the case of an electric motor-powered motorcycle, since the amount of space available in a motorcycle frame is limited. Typically, the main locomotive components of a motorcycle, whether electric-powered or internal combustion engine-powered, are located in an interior volume of the motorcycle frame. This includes the motor, the transmission (if any), the battery pack and the like. In an electric motor-powered motorcycle, the battery pack is wedged within a relatively small space available in the frame of the motorcycle. This configuration limits the consumer's ability to quickly and easily access the battery pack and the battery cells within the battery pack.
Yet another drawback of conventional battery packs for electric vehicles is heat dissipation. Battery packs generate a considerable amount of heat during operation due to the high amounts of current drawn from the packs by the electric motor. Because conventional battery packs are sealed tight and are not built to be easily opened, there is little or no air flow within the battery pack, thereby causing heat to build up within the battery pack during operation. This can be problematic since individual battery cells can become damaged, or their life spans reduced, if they are exposed to exorbitant heat. Operation of a battery cell at high temperatures can also affect the energy efficiency of the battery system.
An additional drawback of conventional battery packs for electric vehicles is the propensity for a sealed pack to retain pressure and debris. Because battery packs generate a considerable amount of heat during operation, an air-tight sealed battery pack that becomes extremely hot can create exorbitant air pressure that cannot be relieved because it is sealed. A sealed container under hazardous amounts of pressure can be dangerous and even lethal to humans. Also, since a conventional battery pack is sealed or nearly sealed, it has the propensity to retain water, condensation, dirt or any other debris that works its way into the container. This can be problematic since individual battery cells can become damaged or short circuited if they are exposed to water, dirt or other debris.
As an example, the commercially available Zero motorcycle, manufactured by Zero Motorcycles, Inc. of Scotts Valley, Calif., utilizes a single, large battery pack comprising a rigid, box-like plastic container that cannot be opened. The container includes a group of battery cells that are wired together in a specific configuration. Specifically, the container includes a set of lithium ion iron phosphate battery cells that together provide 48 volts. As explained above, the main drawback of the Zero's battery pack, besides the relatively low voltage provided, is the inability to easily gain access to the individual battery cells within the container. Thus, the consumer is inhibited from replacing a sole damaged battery cell within the battery pack. Further, the sealed nature of the Zero's battery pack restricts airflow within the battery pack, thereby inhibiting heat dissipation.
Various U.S. patents disclose various frames that allow various forms of access to battery packs for scooters, such as U.S. Pat. Nos. 6,047,786 and 7,255,191. The scooters described in the aforementioned patents, however, require significant disassembly of the scooter body in order to gain access to the battery pack within the scooter. Thus, the aforementioned patents do not disclose adequate solutions to the problem of allowing quick and easy access to individual battery cells within the battery pack of an electric motorcycle. The aforementioned patents also do not disclose adequate solutions to the problem of heat dissipation with the battery pack. Likewise, U.S. Pat. Nos. 3,983,952 and 5,613,569 disclose electric motorcycles including battery systems, but access to the battery pack requires significant disassembly of the vehicle body and access to individual battery cells within the battery pack is limited.
Therefore, a need exists to overcome the problems with the prior art as discussed above, and particularly for a more efficient battery system for an electric motorcycle.